The research proposed is directed toward an investigation of the regulation of a set of coordinately functioning, housekeeping genes, the ribosomal protein (r-protein) genes. The expression of these genes both with respect to the other members of this gene family and with respect to the rRNA genes will be studied. First, several unusual sequences found in and near the Drosophila r-protein gene we have recently isolated will be further characterized. This will include experiments to determine if the short "shared sequence" present on at least six r-protein mRNAs has a role in their translational regulation. The nature and possible transcribability of rRNA gene and spacer fragments and a mobile, rRNA intervening sequence, located near an r-protein gene will be explored. Likewise, the role of these sequences in the control of r-protein transcription and/or translation will be studied. With the isolation of other r-protein genes, the timing and sequence of the transcriptional expression of this set of genes can be observed during normal embryogenesis. Such studies can provide specific data on the induction of ribosome biosynthesis in the early embryo, i.e., the first developmentally regulated zygotic expression of the various r-protein and rRNA genes. Finally, the copy number and chromosomal location of members of the r-protein gene set can be determined. These locations may show correlations with Drosophila phenotypic mutants whose altered r-protein gene expression can be studied. As a long range goal, changes in r-protein gene dosage may be investigated for possible effects on r-protein and rRNA gene expression. Either previously isolated deletions or duplications of chromosomal regions containing r-protein genes or specific P element-mediated insertion of r-protein genes would bring about such gene dosage changes. In total, the results of these studies will be used to evaluate some of the mechanisms that regulate the coordinate expression of the various r-protein genes in conjunction with the rRNA genes, with a view toward understanding the molecular bases for the universal cellular phenomenon of ribosome biosynthesis.